This invention relates to a binder for fastening two panels across a space to each other by forced insertion of a wedge member into a main binder part, and more particularly to a binder of the type which permits the wedge member to be inserted into the main binder part from either of the outer sides of the two panels being fastened.
Heretofore, numerous inventions have been proposed with respect to binders made of synthetic resin and used for fastening panels to each other. Many cases of actual adoption of such binders have been also known. Among these binders, those of one type share a common principle that wedge members are utilized for expanding the main binder parts and the phenomenon of this expansion of the main binder parts serves to fasten given panels to each other. A few actual examples of the use of binders of this type have already found public recognition.
Generally, the binder of the type which makes use of a wedge member has as its basic structure a main binder part formed in the shape of a tube and effects the fastening of two panels by causing this main binder part inserted through the perforations formed in advance in the panels and forcibly inserting the wedge member into the main binder part from either of the opposite ends thereof thereby expanding the main binder part against the edges of the perforations.
The binder using the wedge member is not fastened to the panels only owing to the resilience of its material. It is fastened to the panels because the forced insertion of the wedge member compels the main binder part to expand against the edges of the perforations in the panels. Since this binder can be expected to produce a strong binding force, it is advantageously used for providing powerful union of two panels.
Unfortunately, the binders of this type which have been heretofore proposed are so constructed that the forced insertion of their wedge members into the main binder parts is effected in only one direction. This directional selectivity has entailed a problems that, depending on the location, the binder cannot be used at all or it can be used only with much difficulty.